1. Field of the Invention
The present invention relates to recording apparatus and more particularly to apparatus recording signals on an exchangeable record bearing medium.
2. Description of Related Art
In a recording apparatus of the kind, for example, using a rotary type record bearing medium such as a magnetic disc or drum and recording by a movable head with forming concentric circular or annular recording tracks on the medium, a unit length of information (such as one field or frame portion of a video signal or the like) in each recording track, it is necessary to properly position the head on an unrecorded or recordable part of the medium in advance of the recording if it is desired to record the information while avoiding double or overlapped recording.
With regard to the above, it has been proposed to provide a recording apparatus in which the head is positioned on the unrecorded or recordable part of the medium in advance of the recording by repeating the operation of checking as to whether or not there is a recording at the present recording position where the head is positioned; and by shifting the head to a next recording position if there is a recording at the present recording position. Thus, the recording is enabled only when the head becomes positioned at the unrecorded part of the medium that is, the recording start position on the medium. This technique is disclosed in, for example, U.S. Pat. No. 4,783,707, issued Nov. 8, 1988, assigned to the same assignee of the present application.
When the above described recording apparatus incorporates a control sequence arranged to include, for example, a process of shifting the head to a next recording position either upon completion of recording in one position or at the start of the recording process, the present position of the head on the medium serves as a memory of the next head recording position for the same medium. Therefore, even in cases where the power supply is cut off or where, in the event of a portable apparatus, the power source battery is taken out for replacement or for charging or where the battery voltage drops below a threshold value and becomes unserviceable, it is nevertheless possible to continue proper recording on the same recording medium based on the present head position when the power supply is again switched on or has recovered its voltage, unless in the meantime the head has become shifted to some other position. Such a proper recording position control prevents overlapped recording as well as unwanted unrecorded areas (blank tracks) on the record bearing medium.
However if the record bearing medium is replaced with another medium while the power supply is cut off as mentioned above, the present head position becomes meaningless and is no longer usable as a memory for the new medium. In such case, resumption of recording under this condition results either in overlapped recording or in blank recording tracks. To avoid such problem, the above-stated process of positioning the head for an unrecorded part on the record bearing medium must be carried out every time the power supply is switched on. However, if the record bearing medium has not been replaced, this method is irrational. Besides, this method deprives the apparatus of the ability to obtain prompt recording under all conditions. Further, in the event of a portable apparatus, this method presents a serious problem as it increases the consumption of the power supply battery.
Problems similar to the above are likely to occur also in other types of recording apparatus, such as those which select the recording head according to the properties or kind of the record bearing medium.
In view of the above, there has already been proposed a recording apparatus which comprises memory means to mechanically store recording head position information whenever the recording medium is replaced. In that proposed apparatus, it is possible to mechanically store the information when the recording medium is replaced and to control the repositioning of the head to an unrecorded part of the medium based on the information stored in the memory means so that the head is repositioned only when the recording medium has been exchanged, i.e. replaced. For note, the above-mentioned device is described in Japanese Patent Application No. Sho 60-22633 (U.S. counterpart: U.S. Ser. No. 090,422, filed Aug. 26, 1987, a continuation of application Ser. No. 826,117, Feb. 5, 1986, "Recording or reproducing apparatus", Fukushima et al.) of the same assignee of the present application. Also a head positioning method and recording or reproducing apparatus in which searching is carried out in a direction from the periphery toward the center of the disk is shown and described in Japanese Patent Application No. Sho. 60-22634 (U.S. counterpart: Ser. No. 826,498, filed Feb. 5, 1986, "Head Positioning Method And Recording On Reproducing Apparatus Employing Same", Fukushima et al.).